What does the Bible say about the duality of natures in believers?

In Romans 7, the Apostle Paul expresses the internal struggle of believers who desire to follow God's will but frequently fall short due to their sinful nature. He acknowledges the 'wretchedness' of human condition, showcasing that even justified believers experience a conflict between their new identity in Christ and their old sinful nature. This teaching emphasizes the ongoing struggle with sin and the need for reliance on Christ for deliverance and strength to live according to God's will.